The present invention relates to vibratory conveyors and, more particularly, to a gate for diverting conveyed material from a vibratory conveyor.
An excited frame vibratory conveying system is disclosed by Gilman in U.S. Pat. Nos. 6,079,550 and 6,253,908, which are incorporated by reference herein. A vibratory conveying system consists of a conveying member that is spring mounted on a frame. A vibratory actuator on the frame causes the conveying member to vibrate in a substantially longitudinal direction along the conveying member at its natural frequency. The conveying member is trough-shaped, and material to be conveyed is introduced at one end of the conveying member and moves to the other end as the result of the vibration of the conveying member. Excited frame vibratory conveying systems are particularly suited for conveying particulate bulk material such as powdered, granulated, or comminuted material; small parts such as nuts, bolts, or washers; and other solids comprising relatively small pieces such as various food products.
The utility of a conveying system is greatly enhanced if some or all of the conveyed material can be selectively diverted from the conveyor at a point or points intermediate to the ends of the conveyor. This permits selective diversion of the material to other conveyors, containers, or processes. One method of diverting material from the elongated conveying member of a vibratory conveying system is to provide a gate in the bottom or bed of the conveying member. Generally, the gate comprises an aperture in the bed of the conveying member that is selectively covered by a cover plate. Typically, the cover plate is arranged to slide in a pair of channels defined by guides affixed to the underside of the bed of the conveying member. An actuator attached to the cover plate is arranged to slide the cover plate in the channels to selectively expose more or less of the aperture, controlling the amount of the conveyed material falling vertically through the aperture in the bed of the conveying member. This gate arrangement has several disadvantages, particularly when used with a vibratory conveyor.
First, it is desirable to minimize the mass of the conveying member to reduce the magnitude of the vibratory forces necessary to operate the conveyor. Therefore, the conveying member is characteristically constructed of relatively light-gauge material. However, affixing the guide channels, cover plate, and cover plate actuator to the conveying member increases its mass. Additional mass may also be required to stiffen the conveying member sufficiently to withstand the forces generated by the cover plate actuator. To reduce the mass of the conveying member, the cover plate actuator may be anchored instead to the excited frame or other stationary structure. However, such configuration requires a sophisticated isolation mechanism to ensure that the actuation force to be exerted on the cover plate will not interfere with the vibratory motion of the conveying member caused by the excited frame. Such a mechanism is complex and expensive.
Second, the channels in the guides for slidably supporting the cover plate must have sufficient clearance to permit the cover plate to slide easily therein. Consequently, when the conveying member is vibrating, the cover plate may move in the channels, producing noise and also causing the channels and the cover plate to wear in the areas of contact. The loose fit of the cover plate in the channels, which is exacerbated by wear, permits dust and other fines in the conveyed material to infiltrate into the interface between the channels and the cover plate. The buildup of material in the channels may make the gate difficult to operate in some cases and, in the case of handling food products, may pose sanitary problems. Further, if the cover plate loosens sufficiently in the guide channels, it can move independently of the cover plate actuator merely in response to the vibratory excitation of the conveying member. Uncontrolled motion of the cover plate interferes with the movement of the conveyed material and can substantially degrade the performance of the conveyor. For these reasons, gates of this construction require substantial maintenance, including frequent adjustment of the cover plate relative to the guide channels and removal of the cover plate to permit cleaning of the guide channels. Such gate maintenance is costly and requires that the operation of the conveyor and related processes be suspended for a significant period.
What is desired, therefore, is a gate for a vibratory conveyor that is compatible with the operation and structure of the vibratory conveyor, minimizes wear, is impervious to the effects of infiltration of dust and fines, and requires minimal maintenance.
The present invention provides a gate for a conveyor, for example a vibratory conveyor, that achieves all of the desired characteristics described above. The conveyor for incorporating a gate of the present invention includes a conveyor bed that has a surface portion defining an aperture. The gate includes a cover plate in contact with the conveyor bed but not otherwise constrained to move with the conveyor bed. The cover plate is arranged for movement between a first position covering a first portion of the aperture and a second position covering a second portion of the aperture (e.g., between an open position and a closed position). The gate further includes a loading system (e.g., a combination of elastic elements) coupled to the cover plate and exerting a force urging the cover plate into contact with the surface portion of the conveyor bed defining the aperture. The gate still further includes a carriage assembly coupled to the loading system for moving the cover plate between the first and second positions.
In one aspect of the present invention, the gate is particularly suited for use with a vibratory conveyor. A vibratory conveyor includes a conveyor bed and an excited frame that vibrates the conveyor bed. The carriage assembly of the gate of the present invention includes a base element coupled to the excited frame of the vibratory conveyor and a movable element coupled to the loading system. More specifically, the base element may be formed of a mounting block having a portion defining a bore, and the movable element may be formed of a support rod slidably arranged in the bore to be moveable in a direction substantially parallel to the surface portion of the conveyor bed defining the aperture.
In another aspect of the present invention, the carriage assembly generally prohibits movement of the cover plate in a direction normal to the surface portion of the conveyor defining the aperture bed but permits movement of the cover plate in a direction parallel to the surface portion. To this end, the movable element of the carriage assembly may further include a linear actuator to cause linear movement of the movable element in a direction parallel to the surface portion, such as a pneumatic actuator, an electric actuator, and a hydraulic actuator.
In yet another aspect of the present invention, the loading system may be formed of a plurality of elastic elements, for example a spring plate and an elastomer mount, which are arranged in series to exert a force to maintain the contact between the cover plate and the conveyor bed.
As will be apparent from the foregoing, the gate of the present invention provides several advantages. Because the cover plate is not connected to the conveyor bed of a conveying member, the mass of the conveying member is not altered (increased) by the provision of the gate or any reinforcement required to withstand the forces produced by actuation of the gate. Likewise, because the cover plate and its actuator are not connected to the conveying member, a complex mechanism is not required to isolate the mechanism for actuating the cover plate from the vibratory motion of the conveying member. Furthermore, since no sliding channels are required to support a cover plate, the source of significant wear and noise is eliminated. Still further, because the gate of the present invention is not constrained to the conveying member, any dust or fines that may infiltrate into the interface between the cover plate and the conveying member will migrate out of the interface during relative movement of the cover plate and the conveying member, and thus the gate is self-cleaning. Accordingly, with the gate of the present invention, deterioration of conveyor performance, noise, need for frequent maintenance, and conveyor downtime are substantially reduced.